http是一个（）。
A.高级程序设计语言
B.域名
C.超文本传输协议
D.网址
参考答案：C
---Must we leave the classroom now?
---No, you _____. You _____ leave after the bell rings.
A．mustn't; are allowed to
B．don't have to; might
C．needn't; can
D．can't; are supposed to
硫粉在氧气中燃烧时发出[ ]
A．白光
B．黄色火焰
C．淡蓝色火焰
D．蓝紫色火焰
